37: Sudden Infant Death Syndrome Tied to Serotonin

A study released in July dispelled some of the mystery surrounding sudden infant death syndrome, or SIDS, which kills 2,500 babies a year in the United States.

Jan-Marino Ramirez, a biologist at the University of Chicago, figured out how two aspects of SIDS fit together. First, a child who has the syndrome cannot gasp air. Thus, if a pillow blocks her airway and her brain begins to starve for oxygen, she can’t kick-start her breathing back to normal. Second, in a SIDS child, the neurotransmitter called serotonin often doesn’t bind properly to brain cells. In experiments with laboratory mice, Ramirez and his colleagues distinguished two groups of pacemaker neurons that govern breathing. One group regulates normal breathing; the other group regulates gasping. They found that serotonin regulates the sodium channels that drive the gasping cells. Moreover, problems in sodium channels play a role in epilepsy and heart disorders—both common in children with SIDS. “So we have the missing link,” says Ramirez. “A disturbed serotonin mechanism could lead to disturbed gasping.”

Knowing which cells initiate gasping is just a start. “Now you can ask questions like, What happens if a mother smokes? Does this affect these nerve cells?” says Ramirez. In the meantime, advising parents to put babies to sleep on their backs has proved preventive. Since the “Back to Sleep” public health campaign began in the mid-1990s, the number of annual SIDS deaths in the United States has dropped by 40 percent.